Flat products and long products treated in hot-rolling mills, in order to form sheets, strips, beams, bars, etc., are more and more frequently made from liquid steel contained in a ladle and continuously cast in a mould followed by rolls which allow extraction of the shape obtained by controlled cooling of the steel just sufficient for going from the liquid-metal form into the solid form, the semi-finished product thus obtained on leaving continuous casting generally being at a temperature greater than 1000.degree. C. On account of the high temperature of the semi-finished product, rolling it immediately after casting represents a substantial energy saving compared to the conventional process which consists in storing the semi-finished products before reheating them up to 1250.degree. C. in order to be able to roll them.
In many factories comprising a steel works and a hot-rolling mill, means are employed for carrying out the continuous casting and hot rolling of semi-finished products without systematically passing via a cooling and storage area. However, this approach comes up against three main technico-economic difficulties:
The first is due to the lack of temperature homogeneity of the semi-finished products leaving the continuous casting because of the preferential cooling of the corners and sides of the products, which necessitates top-up reheating and homogenizing of the semi-finished products before rolling. PA1 The second, even more restricting, arises from programmed and especially non-programmed stoppages of the rolling mill in the course of production in order to change a roll or to make corrections to the various settings. During these stoppages, the liquid steel present in the ladles must necessarily be cast in the form of semi-finished products without being able to be immediately rolled it is therefore necessary to be able to store them hot for periods ranging from a few minutes to sometimes an hour or more. PA1 Finally, the third difficulty is of an economic nature since the continuous casting equipment is also exposed to unpredictable maintenance and production factors and undergoes quite lengthy stoppage periods which do not necessarily coincide with those of the rolling mill. In order to improve the profitability of the factories, the rolling mill must in such cases be fed with semi-finished products not coming directly from casting and which, consequently, must be reheated from ambient temperature.
Many known items of equipment may be used either for storage at the casting temperature or for reheating or homogenizing the products coming from casting in particular, the invention described by Patent EP 0,370,916 B1 describes a reheating, holding and accumulating furnace which includes two sets of supporting members and of transporting members, both of which can move in the vertical direction and be located in planes which are below, at the same level as or above the reference plane given by the rollers which enable the ferrometallurgical products to be charged and discharged and, by combining the respective planes of the supporting members and of the transporting members, this being so as to move or not move through one step the products lying on each of the sets of supporting members.
In the furnace described by the aforementioned patent, the movement from charging to discharging is controlled so as either to accumulate the ferrometallurgical products in the first zone defined by he first set of supporting members or to make them pass through this zone as rapidly as possible in order to feed the rolling mill and to create a space available in the furnace for possibly storing therein products coming from the continuous casting in the event of a stoppage of the rolling mill.
The drawback of the prior art resides in the limitation in the transfer speed which may not be equal to or less than the cycle time and to the possible travel of the transporting members. These transporting members follow a rectangular cycle having a total duration of the order of 40 seconds or more, including a first, rise phase which enables the supporting members to be released, a second phase of horizontally transporting and then a third phase of depositing the products which have thus progressed by one step on the supporting members, before the fourth step of return to the rear into the initial position it may be seen that during phases one, three and four, the products do not move, and therefore only a quarter of the cycle is active with regard to progression of the products inside the furnace and, moreover, the step or translation in the horizontal plane of the transporting members is generally limited to less than 0.6 m because of the necessary combination of the vertical and horizontal movements of the mechanism
This limitation may constitute a serious handicap both as regards the production capacity of the furnace and its capacity to free up, for charging purposes, a space sufficient to store products coming from casting if the stoppage of the rolling mill should prove to be longer than anticipated or than usual. Moreover, the slow rate of transfer of the products through the storage zone, which speed represents an advantage when the products charged are practically cold, is a drawback when the semi-finished products are arriving directly from continuous casting since it requires this zone to be held at a high temperature in order to prevent the products from cooling before their entry into the reheating zone. This high-temperature hold is a handicap both from an energy standpoint and an environmental standpoint since, in normal operation, the products coming from continuous casting must reach the reheating zone or even the homogenizing zone as rapidly as possible and, consequently, the storage zone is empty.
The present invention intends to alleviate these drawbacks by providing a satisfactory solution simultaneously to the problem of rate of transfer of the products and to that of holding the storage zone at a high temperature, by making it possible to profit from the fourth phase of rearward return of the transporting members in order to advance the products into the furnace, as will be seen in the following device. Added to the possibility of reheating cold products is the possibility of being able, during running, to modify the residence time of the semi-finished products according to their temperature at charging.
For this purpose, the furnace for storing, reheating and holding ferrometallurgical products, in which the products travel along a displacement path on members placed so as to connect, in the transverse direction, a charging zone and a discharging zone, the reheating and holding zones including, on the one hand, product-supporting members and transporting members placed at a certain distance from the said supporting members and being able to perform a rising movement with respect to these and a horizontal displacement movement making the product advance step by step, is characterized in that the said storage zone furthermore includes supporting and transporting members of the type described hereinabove, at least one set of movable supporting members, independent of the hearth of the furnace, able to move with a horizontal alternating translational movement which is performed during the return phase of the transporting members.
Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an embodiment example thereof, devoid of any limiting character. In the figures: